Cork substitute and aprocess for its production



6, 1 48 E. C.-LATHROP ET AL 2,433,849

CORK SUBSTITUTE AND A Pi'iOCESS FOR ITS I RODUCTION Filed Aug. 21, 1943llllll T555 llluvlll lllllll INVENTORS AE.C.LATHROP S. LARONOVSKY-verting the Patented Jan. 1948 vum'rso N'l OFFICE- coaK suns'rrru'rcAND Araocass r-on ITS PRODUCTION Elbert C. Latlirop and Samuel I.Arononky Peoria, 111., assignors to the United States of America, asrepress Agriculture Application August 21, i943, Serial No. 499,508

3 Claims. (Cl. 106- 122) (Granted under the act of March 3,

amended April 30, 1928; 370 0. G. 75'!) ntedllythesccretaryot' Thisapplication is made under the act of This invention relates to corksubstitutes and more particularly to plastic compositions containingpithy cellulosic materials, and has among its objects the production ofnthetic materials having properties similar to those of natural cork;

the process and apparatus providing for forming sheets of the plasticcompositions, which may be strengthened by added sheets of reinforcingmaterial bonded to either or both sides, or which may be formed with anydesired surface configuration or design; and such other objects as willpended claims, and annexed drawing.

The compressible and elastic properties of natural cork are inherent toa great extent in the structure of this material. Natural cork consistsof an essentially uniform aggregation of minute cells, the livingcontents oi which have disappeared while the walls of the cells havebecome thickened and toughened as a result of the formation in them ofvarious substances of complex nature. walled cells contains air and issealed against all other cells so that the entrapped air cannot moveabout within the material. 7

We have discovered that compositions possessing compressible and elasticproperties similar to those of natural cork can be obtained byenclosingnumerous minute cell-containing particles of comminuted, pithy,natural cellulosic material in an elastic material, thus forming aplastic composition vcontaining numerous microscopic gas cells uniformlydistributed therein and bound together by relatively thick elasticpartitions.

In general, the cork substitutes of'this inven- 7 be apparent from thefollowing description, ap-

Each of these minute, relatively thick tlon are obtained by firstuniformly distributingthe particles containing gas or air cells through-V out a suitable fluid medium and thereafter con fluid medium to aresilient elastic solid. Y

The nature and composition of the fluid media may vary, depending uponthe operating conditions and the p p rties desired in the finalproducts. In general, the fluid medium comprises an elastomer, that is,a substance possessing some degree of residual resilience, dispersed ina suitable solvent or dispersing agent.

, We prefer to use elastomers of a proteinous which constitutes thecontinuous phase of the Ill 2 9 1848 nature, such as gelatin, glue,casein, soybean pro teins or soybean meal, 88 albumin and the like, andto disperse them in an. aqueous dispersing media, including such liquidsas water, aqueous ammonia-borax solution, sodium hydroxide solution,sodium carbonate solution, and certain or ganic nitrogen compounds, suchas urea, various amines, and so forth, the selection of the dispersingagent being determined by the nature of the elastomer, as is well knownto persons familiar with the chemistry of these materials. However,other organic elastomers, including Vinylite" type resins, such aspolyvinylchloride or acetate, may be used by converting them to a fluidstate by means of suitable organic solvents. Solvents for this purposeare well known.

The properties of the. final products may be controlled by additions ofsuch substances as plasticizers and water-proofing agents which, incombination with the elastomers, modify their physical characteristics.For example, paraflin or other waxy materials, such as wax size, rosinsize, high or low melting petroleum jellies, and so forth, may be usedas water-proofing agents,

and proteinous water-dispersible elastomers may be combined withpermanent plasticizing agents, for example, glycerol (glycerine);glycois, such as diethylene glycol, ethylene glycol, butylene glycol,propylene glycol; sorbitol; mannitol; glucose syrups, such as cornsyrup; malt extract: invert sugar; and similar lyophilic agents.

As a source of finely divided particles containing-gas or air cells tobe distributed throughout the fluid medium, we prefer to use comminutedcelluiosic materials of a pithy or fibrous nature containing numerousair-filled interstices, such as paper pulp. wood pulp, and agriculturalresidue pulps including such niaterials as ground comcobs, ground peanutshells, cornstalk pith. bagasse pith, sorgh m pith, or similarforaminous cellulosic substances.

I The particles are added to the fluid medium and uniformly distributedtherein by agitation, for

- example. A heterogeneous mixt re is thus formed The number of aircells'present in the mixture may be further increased by physical and bychemical means. Thus, foaming agents such as soaps, saponin, sodiumhexametaphosphate, sulfonated fatty acids or alcohols, and so forth, maybe added and the mixture subjected to vigorous agitation to. entrap ascells. Similar results can be obtained by addition of blowing agentswhich induce froth formation either by thermal decomposition likeammonium bicarbonate or by chemical reaction like bicarbonates used incombination with weak acids, such as, for example, stearic acid.

The cork substitutes are obtained by converting the fluid medium of themixture to an elastic solid by addition of suitable setting agents,including aldehydes such as Formalin, paraformaldehyde, formaldehyde,andformaldehyde and ammonia, hexamethylene tetramine, tannins, orchromium compounds. such as potassium dichromate, and then drying thesolidified material.

The invention is practiced preferably according to the following generalprocedure.

A mixture comprising the elastomer, the dispersing agent, with orwithout a plasticizer and water-proofing agent, and the foraminouscellulosic material, is agitated, preferably with application ofv heat,until the elastomer is dispersed and an intimate mixture of thecomponents has been effected. The homogeneous mixture thus obtained issubjected to high speed agitation and the foaming or froth-producingagent is added, if one is used. The mixture is then brought to thedesired degree of intumescence by maintaining it under vigorousagitation for the necessary length of time. After adding the settingagent, the mixture may be extruded into desired forms, may be pouredinto a suitable container or mold and allowed to solidify, or it may beformed into sheets by the process and apparatus later set forth. It isthen dried under controlled humidity conditions.

As illustrative embodiments of a manner in which our invention may becarried out in practice, the following example is given:

Example 1 Parts 1. Gelatin (elastomer) 40 2. Water (dispersing agent)200 3. Paraffin (water-proofing agent) 2 4. Glycerine (plasticizer) 305. Glucose syrup (plasticizer) 30 6. Ground peanut shell (particlescontaining gas or air cells) 40 7. Saponin (foaming agent) 0.4 8.Formalin (setting agent) The gelatin is mixed with water and heateduntil the gelatin is melted, forming a gelatin and water solution. Thetemperature may be maintained at any desirable point above the meltingpoint of the gelatin solution, but we prefer a temperature of 60 to 65C., in which range decomposition of the gelatin does not take placereadily. The other materials, with the exception of the Formalin, arethen added to the hot gelatin solution, or all the other components withthe exception of the Formalin may be mixed together in the cold andheated until a uniform mixture is obtained, which is then added to thehot gelatin solution, or a portion of the water, glycerine, and glucosesyrup may be mixed with the gelatin and --.he remainder mixed with thepeanut shell, and ti 1e two mixtures heated separately and then mixedtogether, or the cold peanut shell mixture above procedure or during thewhipping stage to be described later.

After the mixture is all melted and uniform in appearance, it is placedin high speed mixing equipment. If the saponin had not been addedpreviously, it is added at this point. Then the mixture is stirred atany desired speed'above that necessary to keep the paraflln fromcoalescing into large particles as the temperature of the mixturedecreases. As the temperature falls, preliminary gelation of the mixturecommences to entrap air. The amount of air beaten into the mixture canbe controlled by the speed of stirring and by the temperature of themixture, greater speeds and lower temperatures resulting in a largeramount of occluded air.

When the mixture has reached the desired consistency. that is, when itcontains sufficient air. the Formalin is added and. after the latter isuniformly distributed throughout the mixture, the mass is poured into amold, or plated out on a flat surface, or extruded, as desired. Chillingthe 1 mixture immediately after pouring may be desirable, as inextrusion, to set the mixture thermally and thus prevent the materialfrom flowing prior to the setting-up or hardening action of theFormalin, but this is not necessary as the same result may be obtainedby regulation of the consistency of the mixture prior to pouring.

The poured mixture sets-up or hardens sufliciently in a few minutes toenable it to he removed from the mold, surface, or extrusion apparatus.At this stage it is soft, very flexible, and has a rubber-likeelasticity. After drying in a humid atmosphere at any desiredtemperature up to about C., the material hardens somewhat, the degree ofhardening increasing with the time and temperature of drying. On removalfrom the drying chamber and exposure to the normal conditions of roomtemperature and humidity, the hardened material becomes soft andresilient, but

not to the same extent as before drying, and tough. We prefer drying at50 to 65C. to prevent excessive loss of moisture and reduce the time ofreturn to normal conditions. or of seasoning. The material is now readyto be cut, sliced, stamped, or punched into the desired shapes.

The finished material has a cellular structure with a large number oftotally enclosed air spaces. These air spaces are fairly small anduniform and are separated from each other by relatively thick partitionsof the elastic solid material. Thus, the physical structure of thefinished material is similar to that of cork.

The product is very resilient. It may be compressed readily to less than40 percent of its original size without disrupting the structure. Onreleasing the pressure, it returns very rapidly to its originaldimensions. Its resistance to oil is excellent. It can be readily dyedwith any dye or pigment not incompatible with the constituents of thematerial. It can be lacquered, varnished, painted, or coated on thesurfaces.

' Practical bottling tests on beverages bottled in regular operation incommercial plants with this product as the liner in crown seals haveshown that this material is fully as satisfactory as the commercialcork. Bottled beverages sealed with this material and containing up to 5volumes of carbon dioxide (CO2) gas, some pasteurized at 140 F. and someunpasteurized, showed no significant leakage of gas after being truckedfor a week, after heating for one week at F., or

months under normal room conditions. Presfor the correspondingingredients of the formula.

The properties of the final products may be varied within a wide rangeby varying the proportion, of the ingredients used in the composition.For example, increasing the amount of glycerine will result in a softer,more resilient product, while increasing the glucose or ground peanutshell will give a denser and harder material. A ratio of gelatin toground peanut shell of about one is, however, preferred. An increase inthe saponin will yieldasofter material, while a decrease in the amountof water will cause a denser product. The hardness of the final materialwill also increase, within limits, with the larger amounts of taming orsetting agents used.

The following examples illustrate a few of the possible variations ofExample 1.

Example 2 The same ingredients are used as in'Example 1, except that 40parts of commercial acid casein is substituted for the gelatin. Thecasein is dispersed with any of the usual dispersion agents, such assolutions of ammonia, borax, sodium hydroxide, sodium carbonate, ororganic nitrogen compounds, such as urea, various amines, and so forth.We prefer to use ammonia (approximately 10 percent of the weight ofcasein), but any of the above agents, either singly or in suitablecombination, may be used. We prefer to disperse the casein at 60 0.,which is desirable from the standpoint of time economy and low degree ofcasein decomposition, but any temperature from about 20- to 70C. may beused.

When the casein is dispersed, the other ingredients may be added to thedispersion, either singly or altogether, and the same procedure is thenfollowed as in Example 1.

The casein product is very similar in its physical characteristics tothat produced with gelatin orglue, and may be used for the same purposesas the gelatin or glue products.

Example 3 The sameingredients are used as in Example 1, except thatcommercial acid casein is substituted for a portion of the gelatin orglue. The casein may be dispersed and the mixing, whipping, pouring,doctoring, and drying may be carried out substantially as described inExample 2. Thev resulting product has properties similar to thoseobtained with glue. gelatin, and easein products of Examples 1 and 2. v

- Example 4 The same ingredients are used as in Example 1, except thatcommercial soybean protein is substituted for the gelatin or glue. Thesoybean protein is dispersed with the same dispersing agents used forcasein, and the mixing, whipping,

pouring, doctoring, and drying may be carried out substantially asdescribedin Example 2. The

product is very similar in appearance andproper-' ties to the caseinproduct described in Example 2.

. nl 5 V v The same ingredients and substantially the hesive, such asgelatin, glues of various types, albumin, and so forth. "If thecomposition is wet, v

the compositionto, which it will adhere very that soybean protein issubstituted ror part'of the casein. The properties of the product are.

substantially the same as those of the products oi Example 2.

Example 6 The same ingredients and substantially the same procedure areused in Example 1, except that soybean protein is substituted for partof the glue or gelatin. The properties of the product are essentiallythe same as those of the products of Example 3. a

Example 7 The same ingredients are used as in Example 1, except 35percent of all of the ingredients (except water) is replaced by regroundmaterial reclaimed from trimmings of previous samples of the samecomposition. The procedure is the same as used for the fresh ingredientsand the product is very similar to that made under Example 1. a

Example 8 then dried in an oven to remove the volatile organic solvents.A pliable, tough, resilient product is thus obtained. Example 9 A"Vinylite" type resinis dissolved in organic solvents, suitableplasticizers are added, and the whole mixed with suflicient pithymaterial to,

form a still dough. This dough is then milled in a rubber mill atcontrolled temperatures until a smooth sheet is obtained. This sheet,when dry, is flexible, tough, and resilient.

It has been found that when the composition of this invention is platedout upon a sheet=of ordinary paper, such as kraft wrapping paper,

' and is allowed to dry, the paper becomes integral with the compositionand cannot be peeled ofl. from the latter, thus increasing considerablythe strength of plies of the material. Wetting the paper prior'tocontact with the composition will result in better bonding of the twoand in a lower tendency of the material to curl upon drying. This is dueto the fact that the paper swells when wet and then shrinks along withthe cork substitute composition during drying. The paper backing'has butlittle effect upon the pliancy, compressibility, toughness, orresiliency of the composition. In fact, those compositions which tend tobe too short to be used as such are made 7 satisfactorily usable byaddition of the paper backing.

When another sheet of paper, dry or wet, is placed on top of thecomposition, the resulting product has still greater strength propertiesand with no apparent diminution of the toughness,

pliancy, compressibility, or resiliency of the uncoatedmaterial. If thecomposition is dry at the time the top sheet is added, the lattermay beadhered 'to the former with any suitable adthe top sheet, dry or wetted,may be placed upon strongly without the use of an adhesive.

It has also been found that paramn wax, polishing wax, Vinylite" resin,eth'yl cellulose, Celloand similar materials are non-bonding,

that is, do not adhere strongly to this composition. Therefore, corksubstitute composition may be'plated out upon paper or other surfacescoated face of the coated material result in a correspondingconfiguration in reverse on the surface of the composition. Thus, anydesired surface design may be given to the composition.

Any other type of reinforcing sheet having a certain degree ofcapillarity to water may be used in place of paper with equally goodresults. Cotton, wool, silk, or similar materiab'will adhere stronglyto, and form an integral part with, the composition.

The simplest method of obtaining continuous production is to use amoving conveyor. An apparatus designed for this purpose is illustratedin the diagrammatic figure shown in the accompanying drawing.

The ingredients of the composition, with the exception of the tanning orsetting agent, are

' mixed and heated separately or altogether in a vessel l which isprovided with a stirring device ll of any conventional design and with aheatin unit, such as a steam jacket l2, having a solenoid valve l3controlled by a thermostat It. Any

other well-known type of heater may be used.

After thorough mixing at the correct temperature, the fluid mixture isdrained into the smaller vessel l5 through the valve Hi. This smallervessel may be provided with heat and controls similar to those of vesseliii. A high-speed stirrer ",or similar device, for whipping orintroducing air into the mixture is provided in vessel l5. One or morevessels may be used, depending upon the amount of production desired, toallow one vessel to be taken out of service forcleaning without stoppingproduction.

After stirring the mixture until it contains a sufiicient amount of airand the correct temperature has been reached, the tanning or settingagent is added, and stirring is continued long enough to obtain auniform mixture.

The mixture is then drained through the valve I8 and funnel i9 into thebay provided with an exit 2|, the width of which is controlled by adoctor blade 22 to control the thickness of the composition sheet.

If the composition sheet is to be formed without a reinforcing sheet,the partially set mixture is flowed directly onto an endless web 25belted over a pulley 28 which, in this instance, is positioned as shownon the dotted lines in the drawing, and which may be covered with anonbonding sheet with the coating facing outward to insure ease ofremoval of the composition sheet and to imprint any design on itcorresponding to a given design on the non-bonding sheet.

If the composition sheet 21 is to be formed with a reinforcing sheet asan integral part thereof, such reinforcing sheet may be taken from aroll- 28, or in any other manner, to give a continuous ribbon, and ledthrough the bay 20 and onto the endless web 25, receiving the mixturesubstantially in the manner illustrated. In this instance, the pulley 26need not be positioned under the exit 2|, but may be positioned remotetherefrom, as shown in the full lines in the drawing. If it is desiredto pretreat the reinforcing sheet with water, chemical solutions orsolvents, these are placed in a container 20 and the reinforcing sheetis passed under a roller 3| in the container and through a pair ofsqueeze rolls 32 to remove the excess liquid.

In some instances it is desirable to place a second reinforcing sheet onthe opposite side of the composition sheet, in which case the secondsheet may be taken from a second roll 33, through a tank and squeezeroll arrangement similar to that described in reference to thefirst-mentioned reinforcing sheet, and under a roller 34 positioned tolay the second reinforcing sheet on the top side of the compositionsheet, preferably at a point directly above pulley 28.

It may be desirable in some cases to apply a. spray of the setting agentonto the composition sheet after it leaves the bay 20. In this case theagent is applied by means of a sprayer 36 positioned near the exit 2!.Chilling, if desired to thermally set the composition, is effected by acooler, such as a box 36 with a perforated bottom, in which solid CO:may be placed and the stream of cold gas directed onto the compositionsheet in the manner illustrated.

After a period sufficient to set the composition, which may vary from afew seconds to minutes, depending on the temperature, amount of air,amount of setting, and so forth, the composition sheet, with or withoutpaper backing or covering, may be dried in any desired form of drier(not shown) such as a tunnel drier, festoon drier, electric heaterequipped with fans to blow the hot air onto the sheets, or any othercommonly known drying means. The dried material may be stored or shippedin rolls or sheets as desired.

' The following illustrations are given to exhibit the methods ofpreparing the web-backed and special-surfaced compositions.

Illustration 1 A composition was made up according to the formula ofExample 1. The mixing was effected in vessel l0, and the high-speedstirring and incorporation of the setting agent were carried out invessel l5. Shortly after the setting agent had been added, the mixturewas poured into the bay 20. Meanwhile, one end of a paper-reinforcingsheet from roll 28, led under roller 3i, between rolls 32 and throughbay 20, had been stapled to the endless web 25. The machine was startedand the composition, while flowing onto the reinforcing sheet, wasleveled off to the desired thickness by the doctor blade 22, and wascarried-along on the web 25 at the rate of about 7 feet per minute.

At the end of about 1 minute, the composition had set sumciently so thatit did not sag upon the reinforcing sheet when the latter was held in avertical position. A thin spray of 20.percent formaldehyde solution wasapplied at 35, and the, surface of the composition, for a distance ofabout 2 feet beyond 35, was chilled by a current of cold CO2 gas fromthe box 36. The composition as set up on the reinforcing sheet wasallowed to travel on the endless web between two electric heatersequipped with fans until it was dry. It was then seasoned for a fewhours at a relative humidity of about 50 percent, and formed into atight roll.

The paper-backed composition sheet was pliant, tough, and resilient. Acompression pressure of 5000 pounds per square inch was insuilltion 1.

cient to break this material, and its resiliency is attested by anelastic recovery of more than 95 percent.

Illustration 2 A method similar to that of Illustration 1 was followed,except that the paper reinforcing sheet was wetted in a 3 percentformaldehyde solution placed in container 30, the excess solution beingremoved by the squeeze rolls 32.

The product was. similar in all respects to that produced inIllustration 1, but the final sheet showed considerably less tendency tocurl.

Illustration 3 A method similar to that of Illustration 2 was followed,except that a mixture corresponding to that of Example 2 was used.

The operation of the process and the properties of the product weresimilar to those in Illustration 1.

Illustration 4 A method similar to that of Illustration 1 was followed,except that a "Vinylite coated paper was used instead of the reinforcingsheet with the Vinylite" coating next tothe composition. After drying,the Vinylite paper was peeled from the composition very easily, leavingthe latter with a smooth, glossy surface similar to that of-theVinylite" coating.

:. Illustration 5 A method similar to that of Illustration 4 wasfollowed, except that the uncoated surface of the Vinylite paper wasbonded to the composition. .After drying, discs cut from thiscomposition were placed in bottle crowns and tested. All of the testsindicated that this material was at least as good as the compositionspotted in a separate operation, or as good as cork composition seals.

Illustration 6 A method similar to thatof Illustration 1 was followed,except that a second roll of reinforcing paper was used to lay on andcover the composition as it traveled along the endless web 25.

After drying, this laminated product was very resistant to tearing andhad about the same toughness, pliancy, compressibility, and elasticrecovery as the material prepared in Illustra- Ilu'stration 7 The web 25was completely covered with Vinylite paper secured thereon with thecoatin facing outward. The bay 2 0 with doctor blade 22 was placeddirectly over the pulley 26 and the doctor'blade was adjusted for thecorrect height. A composition corresponding to that of Example 1 wasthen plated out directly on the Viny1ite" paper-covered web.

After setting-up, the composition was easily peeled from the paperwithout removing the latter from the web. 1

Illustration 8 A method similar to that of Illustration 7 was followed,except that the composition sheet was dried before it was peeled fromthe paper. The peeling was accomplished with no difliculty and thesurface of the composition next to the Vinylite coating was very smoothand glossy.

Illustration 9 A method similar to that of Illustration 1 was followed,except that the paper was made up by obtained partially set-into a bodyof the desired shape in fastening together various types of paper, thuspresenting various surfaces to the composition. These papers includedplain kraft paper, waxed paper, varnished paper, ethyl cellulose coatedpaper, Vinylite coated paper, vegetable parchment paper, and Cellophane.After drying, the

composition was peeled easilyfrom the waxed,

ethyl cellulose, varnished, and Vinylite" papers,

and from the Cellophaneflbut it could not be separated from the plain orfrom the parchmentized papers. The peeled portions or the compositionsheet had surfaces which were exact replicas, in reverse, of thecorresponding papers.

This innovation in the process and technique of forming our compositioninto sheets greatly increases the practical uses to which it may be put.Seals for crown closures are generally covered with "Vinylite" or other"spot material, which is impervious to. the vapors and liquidsordinarily used for food and beverage purposes, in

order to prevent contamination of the food or beverage with the sealmaterial. Placing our composition on the uncoated surface of a papercoated with Vinylite" or other spot" material, as in Illustration 5,results in a composition sheet with a "spot surface, thus at the sametime strengthening the composition and eliminating the extra operationor spotting." The composition laminated between two layers of paperforms It must not be construed that our invention is,

limited in scope by the preceding illustrations. The latter are givenmerely to exhibit its possibilities. All of the compositions describedabove can be used equally well, depending upon the properties desired inthe final product.

Any type of reinforcing sheet with the desired characteristics may beused. In the case of manufacturing uncoated compositions. the endlessweb itself may be made of material which does not adhere strongly to thecomposition, thus eliminating the necessity of using an additionalnon-bonding sheet.

Having thus described the invention, what is claimed is:

1. A process of forming a cork substitute comprising dispersing gelatinin water at a temperature of about from to C. to produce a fluid medium,mixing paraflin, glycerine, glycose syrup, minute cell-containingparticles of comminuted, pithy, natural cellulosic material, andfsaponintherewith, agitating the mixture to produce uniformity and entrap gascells, adding Formalin, forming the mixture thus produced when it iswhich the particles of peanut shells and the entrapped gas cells areseparated by relatively thick elastic partitions of the materialcomposing the body, and drying the body.

2. A process of forming a reinforced composition sheet; comprisingbonding a sheet ,of the composition, produced by the process of claim 1excepting the forming and drying steps, onto a reinforcing sheet, andthereafter drying the composition sheet.

3. A cork substitute comprising a compressible and elastic compositionhaving a. physical structure similar to cork, made by the process ofclaim 1.

ELBERT C. LATHROP. SAMUEL I. ARONOVSKY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,162,450 Byrnes NOV. 30, 19151,183,694: Sutter May 16, 1916 Number 15 Number

